Telephone system



Jan. 6, 1931. F. APPELIUS TELEPHONE SYSTEM Filed June 27. 1928 2 Sheets-Sheet 1 In1.ren or Jan. 6, 1931, F. APPELIUS TELEPHONE SYSTEM Filed June 27, 1928 2 Sheets-Sheet 2 Patented Jan. 6, 1931 UNITED STATES PATENT OFFICE ERITZ A PPELIUS, OF BERLIN, GERMANY, ASSIGITOR TO TELEPHON-APPARAT-FABRIK E. ZVJIETUSCH &'COMPANY, OF BERLIN-CHARLGTTENBUBG, GERMANY TELEPHONE SYSTEM Application filed June 27, 1928, Serial No. 288,679, and in Germany July 29, 1927.

The present invention relates in general to automatic telephone systems, but is concerned more particularly with a small subexchange working'in conjunction with a main exchange. The number of subscribers lines in the type of sub-exchange above referred to would consist of approximately ten to twenty-five lines and would probably be located in an apartment building or a clubhouse. I 1 7 One of the features of the present inventionconcerns an arrangement for ringingthe desired stationinthe sub-exchange from the main exchange. Talking battery for the subsoribers in the sub exchange is fed from a local battery, which is separated from the main exchange battery, because the line resistance of the main exchange trunk would possibly be too great to provide a good talking circuit for the local subscribers in case talking battery was supplied from the main exchange. The battery of the sub-exchange and that of the central or main exchange are separated byfcondensers so as not to interfere with each other. Moreover, the main exchange should havethe twowires of the trunk line at its disposal for signalling and monitory purposes, without being influenced by the condition of a subscribers line; The condensers and the talking battery which are connected to the trunk line at the sub-exchange are a hinderance when the operator desires to ring back over the trunk line. The present arrangement, however, shows how to overcome this hinderance. Q

In a small system ofthis type, it is often necessary to ring back over i the main exchange trunk line in order to connect a subscriber with another subscriber. of the same sub-exchange. It'is desirable that the calling subscriber engage an exchange line and that the connection to the other subscriber he established over the same exchange line so that two lines are not required for the back calls. Operated in this way, however, makes the sending out of the ringing current even more difficult than described above because the line of the calling subscriber remains connected to the exchange llne when t isnecessary to a ring back on s line- Accor-dinglygfa switching device, which is switched on by the ring be dealt with in an appropriate manner. For

example, ordinary subscribers lines and sub scribers lines having coin box instruments terminating in a sub-exchange have access to the samemain exchange trunk line for extending-calls. Since both types of sub-exchange subscribers use the same trunk line to the main exchange, some means of signalling is required in order for the operator to discriminate between the different types ofsubscribers.

Since the sub-exchange is not large enough for the different types of subscribers lines to be grouped in separate groups, the means for giving the different kinds of signals are, therefore, located in the circuits which are associated ith the subscribers lines.

is customary in telephone practice to inform the calling party when a connection has seen established to a line-which is not connected up or which has been disconnected. The known a rangeinents for signalling the calling party in case the called line is disconnected would be too expensive to be applied to a small system of this type. According to a further feature of the invention, suitable means is provided for signalling the calling party in case the calling party calls line which is out ofservice.

In the drawings, comprising Figs. 1 and 2, there is shown by means of the usual circuit diagrams suficient of the apparatus to enable the invention to be explained and understood. 7

Referring to the drawings, the apparatus shown at the left of the first dotted line of 1 is locatedin the main exchange, while loop, 611 I, n I, choke coil DrlII, earth.

in the sub-exchange.

and VSt and the single plug and dialling cord WVSt. I 0 Sections 2, 8' and 4 of Fig. 1 show a subexchange for semi-automatic working with 17 subscribers lines, 11 to 27, inclusive, of

which only the lines of subscribers 11, 17, and '27 are shown. 7 shown have; access to a common trunkcom- The; subscribers lines prising conductors wand 72 extending'to the main exchange. The station 27 is a coin box station and, therefore, its individual circuit is slightly different from subscribers stations 11 and-17. .All of the coin box stations have the common-relay M connected in series ."with the second winding of the associated line'relay;

' Fig. 2, which should be placeddirectly be low Fig. 1., shows a relay counting or selecting switch-and other relay'circuits located In order to facilitate the ordinary reading, of the circuits, the course of the currents is divided into seven fields; e. g., 4/M signifies the relay M in field 4 and 7/k 1711 represents I thefcont'actk 111 in field 7. V

I Oar/going connection (1) Subscriber No. 11- takes up the receiver. T 11 responds: I Earth, 4/7L II, 07 III, a7) III,.3/t 11 I,subscribers loop,'t 11111, T 11, battery. 3/5 1111 oloses,'before.t 11 I and 2511 III open. '1 "p I.

I 4/D responds:

Bea s r11 11,: 1111, i d 1v, ab 11, D,abI,earth. I

4/(7 I'I'grounds the 0 wire, 4/07 1V opens the short circuitover Ab I, so that Ab responds.

' t/d III and cuit. I V p (2') The battery feed relay ,3/Rresponds: Battery, 3/R, 02111, 32511 III','subscribers M7 III open the starting oir 4/1 III again grounds the 0 wire and opens the short circuit over the 'D relay. 7 (3) 2/7 closes the circuit: f I

i Battery, 2/7 I, m' II, 70 I, a wireto main exchange, 6 II, at I, MAR, AR, earth.

AR and MAR respond. I

In the main exchange a?" II energizes the visible calling signal ASZ while MAR is at'this'time without effect. I

, The operator inthe main exchange insertsan answering plug inthe jack VKZ. AI

jack ofi-normal contact: 707 applies ground over the B relay to the 7) wire in' order to energize the J relay in the sub-exchange.

The relay B with its 7) II contact cuts ofi' relay AR so that the visible signal ASZ becomes de-energized.

(6) In the sub-exchange the relay J responds, battery, J, b-wire to exchange, at III, contact 7%, B, earth. p

2/y' II energizes H." I

Earth, 2/j II, II, battery.

. 4/7L. II grounds the c-wire once more for the correct succession during the later release 2/7t I prepares the dialling circuit, 5/72 III (Fig. 2) prepares the relay selector. I I 6/K II responds overz Earth, 6/72. IV, u III, 07 I, 22 II, K II, batfiery.

ing wires in the sub-exchange.

Conditionof the group station when the (8) f The battery of thesub-exchange is only put in demand slightly as'no selectors are to be used. I I

(9) Release of the group station. The subscriber 11 hangs up the receiver. R retracts 4/7 III short-circuits D, which also be positioned. Therefore even dry cells may retracts. 2/7 I closes the following circuit:

' "Battery, 2/1I,'D1 III, 72. II, I, a wire, jack and plug to signal relay SZ,earth. When the clearing'signal is given-the operator withdraws the plug.- I

2/70 I and 2/70 11- switch through the speak- I (10) In the sub-exchanged retracts when I the operator draws the plug The following operations are due to the fact" that a retraction of the J relay is equivalent to a number impulse. f'Thus first of all comes the number impulse, then the release.

U responds: I Earth, 2/ j II, h I, st I, U, battery. E 1*(Fig. 2) respondsz. Battery, l/sp I,,u II, E 1 Q) III and 7L'III, earth."

El II is connected: I I Earth,'5/h III, 1) III,27L III,.1/e 1 I, E 1

I, p11, 5 27; In,

' II, 5/g III, P, battery.

P responds. JO responds: j Earth, 5/71, III, 4) III, eh III, l/JC II, M II,

asp I, battery. I v

Now the following relays are attracted: T; I

I 11, A6, H, U, E1,'P, Jo.

By responding, releases K over a III. (11) After'a period of delay I-I' retracts; /h II opens the holding circuit forT 11,

'5/Ab II is further held over 5/j0 III.

15/76 III opens the holding circuit for E 1.

J G and P go back to normal. With con- I siderable delay through the short. circuitedi .the:sub-exchange line is again free.

Connection to the subscriber 17 (12) The operator inserts the dialling plug in the selecting ack WKZ. Through the afispring AT is energized thereby connecting the 1) wire to the dialling jack. J responds in the sub-exchange:

Battery, J, b-wire, at III, b-spring in the dialling jack, dialling plug W-ST, dial. switch N Sch, earth.

,- winding 6/J GI and /jc III holds Ab II attracted.

EI connects itself: Earth, 5/h III, 1; III, 2h III, 1/0 1 I,

E 1 II, 5/ 9 III, P, battery.

P responds, 1/3) I cuts off E 1 I winding.

() First closure in the number switches.

J again responds. U retracts, because Q/j I I: opens the energizing circuit. Si responds.

Battery, l/StI, g I, a I, p. I, 5/eh III, '2; III or 1 II, 71, III, earth.

(16) End of the tens selection.

During the pause between tens and units selection, J remains energized and U re.-

. tracted.

Therefore in the sub-exchange the relay l/J G, retracts, because l/u II opens the'energizing circuit for sufficient time.

(17) Now Z 1 responds.

Earth, 5/72, III, e III, 6/ III, jc II, WWV II, 61 II, Z 1 I, battery.

Z1 connects itself.

Earth, 5/h III, 1; III, 6/21 I, Z1 II, ZI-I, battery.

ZII responds: 5/272. III opens the holding circuit for'E 1,'St and P, so that P retracts With retarded action.

5/VVW responds:

Battery, 5/WVIV, 6/271 I, p III, 5/1; III, 7: III, earth.

WVW connects itselfover 5/1010 I.

Condition in the sub-exchange: relay I H, Z1, ZH, IVW are energized.

(18) Unitsselection 7..

First numerical selection interrupter: in;

the number switch.

J- retracts; U responds. Earth, Q/j II, .71. I, 86. I, U, battery- JG, E1. and; A611" respond:

Earth, 5 III, @111, ww'Leh: n1, l/JO II, a II, 829 I, battery.

Earth, 5/71 III, e III, ww I, ah III,.1/p;I, E1 I,.'u II, 87) 1, battery.

Earth,.5/jc III, AbII, battery.

E 1 connects itself.

Earth, 5/h III, 0) III, um: I, ah III,,1/e 1 I, E 1 II, 5/9 III,.P, battery.

P'responds.

(19) Firstclosure of circuit in dial switch.

J again responds- U retracts. not let the armature retract as; it. is slow acting.

St responds.

Battery, l/St I, g I, a 1,4) I,.5/zh III, row I, o III, h III, earth.

The following relays: are now energized A72, (LI-I, Z1, ZH, WWV (JG) E 1,1152% (20) Second interruption of'impulse current.

.I' retracts. St IIis heldand GD energized:

Earth, 2/ II, it I, st I, St 11, G Lbattery.

G connects itself over:

wwI, 42 III, h III, earth.

E2. responds.

Battery, l/sp I ,.g-II, st, II, EQI, e 1 I, 5/270 III, row I, '0 III, h II'I',.earth.

(21) Secondclosure, of current.

J again responds- St retracts, because the winding l/St I1is opened at g I and the winding Q/St II at jII.

E 1 retracts, because the holding current for E 1 II is interrupted at 5/ III (energized) and at st III (at rest).

The following relays are energized:

(22) Third-interruption.

J again retracts. U responds;

Earth, Q/j'II, h I, st I, U, battery.

1/% I'opens the holding circuit for G II so that G retracts.

E3 responds:

Battery, 1/81) I, a II, E 3 I, e 2I, 5/272 III, wwI, Q) III, h III, earth.

E3 connects itself.

Earth, 5/h III, '2) III, wwI, 2h III, l/e I, E S II, 5/9 III, P, battery.

(23) Third closure.

J again responds. spends.

Battery, l/St I, gI, uI, pI, fi/ah I-ILwwI, 1) III, h III, earth.

E2 retracts,.because 5/9 III at. rest and 5/56 III opens the holding current for E 2 II.

The following relays are energized: Ab,

U retracts. St re- This isthe same condition as durin the.

JG does first closure only that is energized instead of E1. I V

(24) With the succeeding impulses the condition at the end of 23 occurs with the make of the current after odd figures with the difi'erence that E5 or E7 is energized and withthe current making after even figures, the condition at the end 01521 is es tablished with the difierence that E4, E6 or E8 is energized instead of During the 7th make the following relays are'energize Ab, J, H, Z1, ZI-LVVW, (JG) P, St, E7. (25) Coupling to subscribers line 17. As-J remains energized, i. e. U or G no longer responds, l/JC retracts after a period of'retraction The relay K responds. Battery, 6/K I,/ww II, jc II, 7 III, 5/0 III, k'III, earth. 7 V

K connects itself. I I Battery, 6/K ILEILYM III, h IV, earth. 2/161 and 2/70 II switch through the speaking wires 7 flu IIIcloses the energizing circuit for the line relay 7/T 17. Earth, 7/70 III, e 7 III, T 17 I, e1 III, m0 III, V, battery.

V and T 17 respond. V releases the selector and T 17 connects the subscribers loop to the speaking connecting line.

(26) Release of'the selector. g

5/oI short circuits P. When P retracts the holding circuits for E7, G or St, Z1, Zh and IVVV are opened by 5/10 II (retracted) and 5/4) III (energized); Thus V also becomes de-energized and retracts after a certain time and with 5/? III makes the selector again ready for reception.

(27 The holding circuit for T 17 is closed over 3/2? 17, II:

Battery, 3/T-17 II, t 17 11, 4 0; W, a?) 1i, D, h II earth.

D responds. l/(Z 1V opens the short circuit over Q/AJ) I, which also responds it it had retracted since the retraction of JC. l/ab II short circuits D, which again retracts. Condition after the selector is cut off. 3

Following relays are energizedpJ, T 17 Ab. I i T (28) Ringing. I

The operator in the main exchange puts the connecting plug into the-speaking jack VKZ. Earth therefore remains connected to the 6 wire over the relay B. Then she withdraws the selecting plug from the ack WIU.

The change of plug has no'infiuence on the sub-exchange. Then the operator sends out alternating current by throwing the ringing key R. The relay J is notreleased'by the alternating current. In thecommunity station the ringing current energizes the relay I/V.

3/20 II energizes the ringing relay NI 2/72 II opens the branch tothe choke. 3/n I and 3/72 IIIbridge thecOndenSersCIand C2, so

r In the ringing pauses 3/? III connects the feed relay R and 3/92 I connects the chokes Dr 1 I to the subscribers line. I

(29) Subscriber T 17 answered. In a ringing pause R responds.

Battery, 3/3, a III, subscribers loop, a I,

choke Drl I, earth.

2/1" I, cuts off the battery from the a. wire. This act deenergizes the supervisorysignal SZ in the cord ofthe main exchange, whereat the operator recognizes the answer. 1/?" III opens the short circuit over D, which again responds without any consequences for the moment. When the subscriber replies t e following relays are energized: J, H, K, T 17 D,A.Z ,R.

30) Clearing signal to the exchange. The subscriber l7 han s up the receiver, retracts, 1/? III short circuits D, which retracts without further consequences .for the moment.

2/1" I closes the circuit:

Battery, 2/? I. Dr 1 II, a t-II, 70. I, a wire, a sprin of jack VKZ, connecting plug visible signal-BE, earth. 1

' (31) Release.

The release'goes on exactly as with an outgoing connection, as in (9), (10) and (11).

Calling back z'nto its own community em change the community ex- I subscriber to hang upthe receiver. R retracts.

4/ III short circuits D, which retracts without further efiect, I p 1 2/1 I applies battery or" 2/37" 1 IIto the a wire, whereupon the clearing signal'appears in the main exchange. Nowthe operator knows that the calling subscriber hashung up the receiver. Now she inserts the selecting plug in the selecting jaclz VVKZL The 5 wire is therefore grounded over thedialswitch,

whilst the 6 wire to the answering cord; is interrupted through relay AT. 7

(34f) Tens select1on1.

With the breaking of the impulse current.

J retracts; U'responds.

Earth,2/j II, 7L1, s25'1,-U, battery.

S/u III opens the holding circ uit ILwhich retracts,;in order not to-disturb the numericalselection by the bridges'lying behind the 2/72I andQ/lo II. l/uII letsE 1 andJC respond:

Battery, sp .l/n II, E 1 I, ,p I, .5/zh III, '0 III, h III, earth.

Circuit forJGi' Battery, 8p .I,.1/u II,.JC II, 5/2h III, p III, "h III, earth.

.Elconnects itself:

.Earth, 5/hIII, '0 III, 27L III, 611,13 1 II, 5/;(7 II -I,.P, battery.

Presponds. During the succeeding closure of long duration in the dial switch, J re- 5 .sponds. U retracts and as the :closure lasts a longtime, JG also retracts.

The tens relay Z 1 responds:

Battery, 6/Z :1 I, e 1 II, we!) II, y'o II, p III, 5/pII'I, h III, earth.

.Zl connects itself and energizes ZI-I.

Bittery, 6/ZH, ZlIL-zll, 5/1; III, h III, cart v .5/zh III opensthe holding circuitfor E 1, .JC-and :P whichretract. WW responds:

Battery, 5/WW, 6/zh I, p III, 5/4) III, -71. III. earth.

WW connects itself overi'5/wwI.

Conditionafter the tens selection.

.Following'relays are energized J, I-I,"T .12,

(35) Units selection.

This conditionis the same asat the corn- .mencement of (18) except that'the relay T 12 .and A?) are energized.

These relays have no influence on the succeeding units selection. The seventh'closure ofcurrent-creates the condition as described in 24.

Coupling of the line 17.

.After a time, JO retracts. .Kand T 17respond I as described in (.25).

(.-R-)elease of the selector=as described under 25 -(36) After the end of the numerical selec- .tion, -the operator inserts the connectingplug in the connecting jack VKZ and then withdraws the selecting plug.

(37) During the back ringing, both subscribers are called. The calling subscriber must only take uphis receiverhowever, when the called subscriber has answered. In order to identify this condition, the call, duringthe back ringing connection, iseffected by short interruptions, say every three seconds.

: 5 Should the calling'subscriber place himself in circuit too'soon, i. e. beforethe called subscriber has answered,-the operatortells him to hang up his receiver and calls again.

The operator .must therefore ask the first so replying subscriber what his telephone numb.er is,.in order to'ascertain whether it is the called subscriber. In view of the small number of back ringing connections-this method of working should be permissible. In exchange withlarger batteries (.24volt accumulators) the call and the cutting oif of the call may take place absolutely automatically .by using a special cord for ring back connections in conjunction with a three-seconds ringing device. The clearing signal in the connecting cord disappears when one of the subscribers takes up his receiver and only appears again when both have hung up.

(38) Release.

When after both subscribers have hung up their receivers, the operator releases the Outgoing call from a coin boa: instrument The T relays of lines going to coin box instruments are taken to battery over the relay M. As soon as the locking circuit of the T relay is closed over D and Ab, relay M is operated and inserts the high resistance Q/Wz' inthe calling circuit to the main exchange. Belay AR at the main exchange cannot be operated over the resistance Q/Wz'. Hence only the coin box instrument calling relay MAR is energized, and the coin box instrument call indicator MASZ is operated over earth, or II, mar II to indicate the call. In this case the operator may only establish the connection after payment. The current that does not operate the relay AB is determined by the resistance of the line. The establishment of the connection and the release of the group take place in the same manner as for an ordinary subscribers line.

Wrong connection to a tens group that is blank If during the tens selection a number is dialed that does not correspond to the group, for example 30, 40, 50, etc., the relay Sp is operated over 6/6 instead of the tens relays Z1 or Z2. The contact 1 /sp I is opened and thereby disconnects the chain of E relays. Therefore a succeeding numerical selection has no effect on the selecting device and the relay Sp remains energized. The contact 8/8?) II closes the following circuit:

Battery, 3/D1 2, sp II, busy relay l/Bos, bos II, earth. The busy relay begins to buzz and this buzzer tone reaches the a-lead:

Earth, l /bee II, Bee, sp II, a-lead to the main exchange.

This busy signal notifies the operator at the main exchange of her error and she withdraws the plug from the jack. Thereby the relay J is deenergized at the sub-exchange and the sub-exchange releases in the ordinary manner. I

. Selecting a'subscm'bers line that as not I connected up The subscribers numbers are so distributed that the number of subscribers connected to each tcns group is the same. Hence for l t lines the'numbers 11 and 21, 12and 22 up to 17 and 27 are used. The line relays for the unused lines 18and 28 to 10 and 20are not installed, in orderto reduce to a minimum the apparatus at the sub-exchange. The contacts 6 III of the selecting relays E for the not connected up numbers are combined and are taken'to the relay Sp. These are the contacts e 8 III, e 9 III, e 10 III in field 7 of the drawing. If during the numerical selection one of the three relays E 8,111, 9, or E 10 3e energized, the relay Sp is operated, and this has the same result as that described for a wrong tens selection. I I What is claimed is:.

1. In a telephone system wherein sub scribers lines terminating'ina sub-exchange are arranged to beconnected to a main exchange "trunk line terminating in an operators position at the main exchange and arranged to signal the operator thereat responsive to the initiation of a call, means for main taining the calling'subscribers line in operative connection with said trunk line after the calling subscriber replaces his receiverin response to such request by theoperator when calling a local subscriber, means in the subexchange controlled by impulses sent over said same trunk line from the operators position forconnecting a desired called subscribers lineto said trunk line, means con-- trolled by the operator for signalling both the calling and called subscriber over said trunk line whereby the talking circuit between the calling and called lines is completed over a portion of said trunk line when both subscribers remove their receivers, and means controlled over said trunk line from the main exchange for releasing said connection after both subscribers have replaced their receivers.

2. In a telephone system, amain exchange, a sub-exchange, a trunk line comprising .two talking conductors connecting said exchanges, two classes of subscribers lines terminating in said subexchange, signals at the main exchange for designating the class of line calling, a'relay 1n saidsub-exchange common to all subscribers lines of one class and operated whenevera subscriber in such class initiates a call, a circuit including contacts on said relayand one of said talking conductors for controlling the operation of said signals, and means in said sub-exchange controlled over said other talking conductor for opening said circuit whenever the call is answered.

the main exchange controlled over only one of 1 the talking conductors of said trunk line for designating the class of line calling,"and a relay in said sub-exchange common to all subscribers lines of one class for determining which one of said signals is to be operated, said relay operated whenever a subscriber of said one class initiates a call.

4. In a telephone system, a main exchange, a sub-exchange,a trunk line connecting said exchanges, two classes of subscribers lines terminating in said sub-exchange, a line circuit for each subscribers line for initiating a call over said trunk line, means common to and included in thesaid line circuits ofall subscribers lines of one class,signals at the main exchange controlled over said trunk line for designating the class of line calling, and means controlled by said first meansfor op.- erating the signal corresponding to the class of the line which is calling. I

5. In a telephone system wherein two classes of subscribers" lines terminating in a sub-exchange establish calls over the same trunk to a main exchange, 'signals at the main exchange controlled over saidtrunk line for designating the class of line calling, and a relay included in the individual line circuit of each subscribers line of one class for determining which one of said signals will be operated, said relay common to all the sub scribers lines of said one class.

6. In a telephone system, a main exchange, a sub-exchange, a trunk line comprising only two talking conductors connecting said exchanges, a pluralityof subscribers lines terminating in said sub-exchange, a relay counting switch in said sub-exchange, means for transmitting impulses over only one of said conductors to set said switch in various positions corresponding to the telephone numbers of desired called subscribers, means operated in case the switch has been'setin a position corresponding to one of said subscribers lines for directly connecting said subscribers line with said trunk line, a source of signalling current and a relay insaid sub-exchange, and means for operating said relay to connect said source directly with the other of said conductors in case sald switch has been set in does not correspond to a causing said switch to select and directly connect the desired subscribers line to said trunk line, and means operative in case the calling party dials a telephone number which does not correspond to a working subscribers telephone number for causing said switch to connect a tone signal to the other of said conductors.

8. In a telephone system, amain exchange, a sub-exchange, a trunk line connecting said exchanges, a plurality of subscribers lines terminating in said sub-exchange, a relay selective switch in the sub-exchange, means responsive to a calling party in the main exchange dialling the telephone number of one of said subscribers lines over said trunk line for causing said switch to directly connect such subscribers line to said trunk line, and

- means responsive in case the calling party dials a telephone number which does not correspond to any subscribers telephone number for causing said switch to connect a special tone signal to said trunk line.

9. In a telephone system, a main exchange, a sub-exchange, a trunk line comprising only two talking conductors connecting said exchanges, a plurality of subscribers lines terminating in said sub-exchange, a relay counting switch in said sub-exchange, an impulsing relay in said sub-exchange connected to one of said conductors, means for transmitting impulses over said one conductor to said relay, means controlled by said relay responsive to the receipt of said impulses for setting said switch in a position corresponding to the telephone number of the desired called subscriber, means controlled by said switch in operated position in case said switch has been operated to a position corresponding to a working subscribers line for directly connecting such subscribers line with said trunk line, a source of signalling current and a signalling relay in the sub-exchange, means for operating said signalling relay to connect said source with said other conductor in case said switch has been set in aposition which does not correspond to a working subscribers line, and means for controlling said impulsing relay over said first conductor to release the operated apparatus in the sub-exchange.

In witness whereof, I hereunto subscribe my name this 24th day of May, A. D. 1928.

FRITZ APPELIUS. 

